There are brake systems already in use which, with a brake disc fastened to a wheel of a railway vehicle, slows or stops rotation of the wheel by pushing a sliding-contact member against the brake disc. In such brake systems, a large amount of frictional heat arises at the brake disc during braking. Therefore, in some cases a structure is adopted in which a plurality of radial fins that extend in the radial direction are provided on the rear face of the brake disc to thereby cause air to flow between the brake disc and the wheel by rotation of the brake disc and thereby release heat from the brake disc.
In the case of a brake disc that has a plurality of radial fins, when the brake disc is mounted in a rapid-transit railway vehicle and a wheel with the brake disc rotates at a high speed, a large amount of air flows between the brake disc and the wheel and generates a large noise. Therefore, Patent Literature 1 proposes to provide a circumferential rib that imparts resistance to air flowing between a plurality of radial fins and adjust an opening area between the radial fins by means of the circumferential rib, for suppressing the amount of air that flows between the plurality of radial fins to thereby reduce noise.